After receiving 4 rejections, I learned some valuable information. Currently, the IRS still has not processed 7 million 2019 tax returns. If this applies to you, even though your 1040 has a specific AGI, the IRS has it as zero.
To confirm this most likely applies to me, I created an IRS account to see my tax transcripts. For the year 2019, instead of the transcript, it has a "Verification of non-filing letter for the year" which "provides proof that the IRS has no record of a filed Form 1040-series tax return for the year you requested."
I went back to my 2020 return and entered zero for the AGI and re-efiled. The IRS accepted it within 5 minutes.
This more than likely explains why I only received the first stimulus and not the second or third.
I of course will contact the IRS to further confirm for my scenario, but I thought this might help some people.
